Her decision to leave the company proved to be an 'expensive' mistake. [=a mistake that caused her to lose a lot of money]
They live in an 'expensive' neighborhood. [=a neighborhood in which houses, apartments, etc., cost a lot to buy or rent]
an 'expensive' shop [=a shop that sells expensive things]
(..) You're gonna make a great dad. Yeah, Ross. You and the baby just need better blocking. Oh. Have either of you ever been to the Rainbow Room? Is it expensive? Only if you order stuff. I'm taking Ursula tonight. It's her birthday. - Whoa. What about Phoebe's birthday? - When's that? (..)1995 TvShow: Friends Title: The One with Two Parts: Part 2 Season: 1 Episode 17